Motor vehicles having a hybrid drive unit have, in addition to an internal combustion engine, at least one electrical machine which is able to be coupled to the power train of the motor vehicle. During generator operation, this electrical machine provides electrical energy which is stored in an energy accumulator, formed by the vehicle battery, until it is supplied to a consumer of the motor vehicle. During motor operation, the electrical machine alone or together with the internal combustion engine is used for the propulsion of the motor vehicle, in the latter case it being used to absorb the fluctuations in the output power of the power train, so that as far as possible the internal combustion engine is always kept in a consumption-optimized operating range in order to increase the efficiency of the drive and to reduce the environmental impact due to pollutants of the internal combustion engine. In order to ensure that sufficient energy is available to supply the electrical machine and the other consumers of the motor vehicle, the state of charge of the vehicle battery is continuously monitored and, as a rule, kept at a predefined constant value. In the event of a drop in the state of charge below this value, a charge controller of the battery requests electrical energy from the electrical machine which thereupon goes into generator operation in order to recharge the battery. However, this battery recharge is unnecessary when the motor vehicle is decelerated shortly thereafter and substantial amounts of kinetic energy of the motor vehicle are converted into electrical energy by the electrical machine and fed into the battery. While the vehicle is decelerating, the entire kinetic energy of the motor vehicle usually cannot be recovered; as a rule, however, a substantial portion can.